1. Field
The present disclosure relates to a thermoelectric material having a high performance index and a thermoelectric module and a thermoelectric device including the thermoelectric material, and more particularly, to a thermoelectric material having a high Seebeck coefficient, high electrical conductivity, and low thermal conductivity and a thermoelectric module and a thermoelectric device including the thermoelectric material.
2. Description of the Related Art
In general, thermoelectric materials are materials that are used in active cooling, waste heat power generation, and other similar applications of the Peltier effect and the Seebeck effect. FIG. 1 schematically shows thermoelectric cooling using the Peltier effect. Referring to FIG. 1, the Peltier effect is a phenomenon in which, when a DC voltage is externally applied, holes of a p-type material and electrons of an n-type material are transported to cause heat generation and heat absorption at opposite ends of both the n-type and p-type materials. FIG. 2 schematically shows thermoelectric power generation using the Seebeck effect. Referring to FIG. 2, the Seebeck effect is a phenomenon in which, when heat is supplied from an external heat source, current-flow is generated in the material while electrons and holes are transported to cause power generation.
Active cooling that uses such a thermoelectric material improves thermal stability of devices, does not cause vibration and noise, and does not use a separate condenser and refrigerant, and thus the volume of devices is small and the active cooling method is environmentally-friendly. Thus, active cooling that uses a thermoelectric material may be applied to refrigerant-free refrigerators, air conditioners, a variety of micro-cooling systems, and the like. In particular, when a thermoelectric device is attached to memory devices or other computer devices, the volume of the memory devices may be decreased and the temperature of the devices may also be maintained to be uniform and stable, especially in comparison with a conventional cooling method. Thus, the memory device or other computer device may have improved performance.
Meanwhile, when thermoelectric materials are used in thermoelectric power generation by using the Seebeck effect, the waste heat extracted by the thermoelectric materials may be used as an energy source. Thus, thermoelectric materials may be applied in a variety of fields that increase energy efficiency or reuse waste heat, such as in vehicle engines and air exhausters, waste incinerators, waste heat in iron mills, power sources of medical devices in the human body using human body heat, and other applications.
A dimensionless performance index ZT, defined as shown in Equation 1 below, is used to show the performance efficiency of a thermoelectric material.
                    ZT        =                                            S              2                        ⁢            σ            ⁢                                                  ⁢            T                    k                                    Equation        ⁢                                  ⁢        1            where S is a Seebeck coefficient, σ is an electrical conductivity, T is an absolute temperature, and κ is a thermal conductivity of a thermoelectric material.
To increase values of the dimensionless performance index ZT, there is a need to develop a material having a high Seebeck coefficient, high electrical conductivity, and low thermal conductivity.